It is known that certain biologically active compounds are better absorbed through the oral mucosa than through other routes of administration, such as through the stomach or intestine. However, formulations suitable for such administration by these latter routes present their own problems. For example, the biologically active compound must be compatible with the other components of the composition such as propellants, solvents, etc. Many such formulations have been proposed. For example, U.S. Pat. No. 4,689,233, Dvorsky et al., describes a soft gelatin capsule for the administration of the anti-coronary drug nifedipine dissolved in a mixture of polyether alcohols. U.S. Pat. No. 4,755,389, Jones et al., describes a hard gelatin chewable capsule containing nifedipine. A chewable gelatin capsule containing a solution or dispersion of a drug is described in U.S. Pat. No. 4,935,243, Borkan et al. U.S. Pat. No. 4,919,919, Aouda et al, and U.S. Pat. No. 5,370,862, Klokkers-Bethke, describe a nitroglycerin spray for administration to the oral mucosa comprising nitroglycerin, ethanol, and other components. An orally administered pump spray is described by Cholcha in U.S. Pat. No. 5,186,925. Aerosol compositions containing a hydrocarbon propellant and a drug for administration to a mucosal surface are described in U.K. 2,082,457, Su, U.S. Pat. No. 3,155,574, Silson et al., U.S. Pat. No. 5,011,678, Wang et al., and by Pamell in U.S. Pat. No. 5,128,132. It should be noted that these references discuss bioavailability of solutions by inhalation rather than through the membranes to which they are administered.
Zolpidem is a imidazopyridine having the structure shown below:

The chemical name for zolpidem is N,N, 6-trimethyl-2-p-tolyl-imidazo[1,2-a]pyridine-3-acetamide
Zolpidem is a non-benzodiazepine sedative-hypnotic and is used to treat insomnia. To treat insomnia, zolpidem is typically administered orally at a dose of between 10 and 25 mg. Typically zolpidem is administered as the tartrate salt, i.e., N,N, 6-trimethyl-2-p-tolyl-imidazo[1,2-a]pyridine-3-acetamide L-(+)-tartrate (2:1). Following discontinuation of zolpidem the beneficial effects on sleep can last for up to a week. Tolerance and physical dependence is only rarely observed with zolpidem. (Goodman and Gilman's The Pharmacological Basis of Therapeutics, 9th ed., pp. 471-472).